How to repair a polypropylene gas tank

Written by c.l. rease
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You cannot repair a damaged polypropylene gas tank with epoxy or a plastic tank repair kit, because gasoline will quickly dissolve the epoxy and the leak will reappear. Polypropylene is a thermoplastic, which means that you can use heat to melt the plastic and create a permanent repair in the polypropylene gas tank. To heat the polypropylene, you need to use a specialised tool that has a controlled heat output. This reduces the chance that you will scorch the surface of the gas tank, which will result in an ineffective repair.

Skill level:

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Things you need

  • Vehicle repair manual
  • Mechanic's tool set
  • 2 pts. acetone
  • 1-gallon plastic bucket
  • Clean rags
  • Plastic welder with speed-welding tip
  • Polypropylene filler rod
  • Side cutters

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  1. 1

    Drain the gasoline from the polypropylene gas tank and remove the damaged polypropylene gas tank from the vehicle, per the vehicle's repair manual, with the mechanic's tool set.

  2. 2

    Remove any gasoline residue from the gas tank by pouring 1 pt. of acetone into the damaged gas tank, swirling the acetone around in the gas tank and pouring the acetone into the 1-gallon plastic bucket.

  3. 3

    Pour a small amount of acetone on a clean rag and wipe the damaged area of the polypropylene gas tank to remove gas residue from the outside surface of the gas tank.

  4. 4

    Allow the gas tank to dry thoroughly before proceeding.

  5. 5

    Plug in the plastic welder, turn the heat control knob to 302 degrees Celsius and set the plastic welder aside to preheat.

  6. 6

    Set the polypropylene gas tank with the damaged area facing up.

  7. 7

    Place the speed tip against the damaged gas tank. When the surface of the damaged area starts to melt, drag the speed tip across the damaged area to tack-weld the surface of the polypropylene.

  8. 8

    Align the speed tip with the start of the tack weld, slide a length of polypropylene filler rod into the speed tip, and push the filler rod into the melting tack weld.

  9. 9

    Drag the plastic welder along the tack weld while pushing the polypropylene filler rod toward the surface of the gas tank.

  10. 10

    Clip the polypropylene filler rod with the side cutters when you reach the end of the tack weld. Slide the speed tip over the cut filler rod to fuse it to the surface of the gas tank.

  11. 11

    Lay multiple passes of filler rod if the damaged area of the polypropylene gas is wider than one width of filler rod.

  12. 12

    Allow the welded area to cool thoroughly before you reinstall the gas tank in the vehicle.

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